Drafting instrument



Patented Sept. 30, 1947 UNITED STATES PATENT opp-ICE 1 y 2,428,310 7 DRAFTIN G INSTRUMENT Ralph AllisonHendry, Truro, Nova Scotia, Canada 3 Claims.

My invention relates to improvements in draft view in vertical section taken on Figure 4, and view in perspective of the anchor graduated in degrees from the 45 to the 90 radius lines 6, 1, as shown H are drilled in the body I at the the tangent lines l0, and similar approximate points of intersection radius line 8 at I. Holes extremities of holes at the of the arcuate lines 9 and the radius lines 6, I.

strument, the center pin M is first placed in the anchor block l3 and with the block held canted on a work sheet, or the like, so that the point of the pin I4 is visible beneath the block, said pin is centered on a selected center point, the block and pin then straightened up so that the anchor anchor block l3 so that the body I may be swung about the centered anchor block I4 flat on the work.

The arcuate lines 9 are designated by suitable degree and minute markings indicating the degree of curve of the arcs to a predetermined scale as shown in Figure 1.

It is not believed to be essential to a proper understanding of the invention to describe all possible uses of the same. The uses described in the following are deemed sufiicient.

To lay 01f an angle from a given point on tangent, the term tangent meaning any straight portion of a center line, following railway and highway practice, center the anchor block I 3 on the given point and anchor said block on center,

Other uses of the instrument Will be apparent.

The foregoing will, it is believed, suflice to impart a clear understanding of my invention with out further explanation.

Manifestly, the invention as described, is susceptible of modification without departing from the appended claims.

What I claim is:

1. In an instrument of the class described, a transparent body of substantially ninety degree segmental form provided with an apertured axisforming tab, a bushing fixed on said tab conaperture in the tab, an anchor same to the work in centered position.

2. In an instrument of the class described, a

transparent body of substantially ninety degree segmental form provided with an apertured axisforming tab, a bushing fixed on said tab concentrically of the aperture in the tab, an anchor block fitting in said bushing and adapted to form a bearing about which the bushing and body may be rotated on a piece of work, means to center said anchor block relative to a selected point on the work, and means on said block to attach the same to the work in centered position, the firstmentioned means comprising a centering pin, block having an axial bore extending therethrough through which the pin is adapted to be extended.

3. In an instrument of the class described, a.

transparent body of substantially ninety degree segmental form provided with an apertured axisblock fitting in said bushing and adapted to form a bearing about which the bushing and body may be rotated on a piece of work, means to center said anchor block relative to a selected point on the work, and means on said block to attach the same to the work in centered position, the lastmentioned means comprising bottom pins on the block adapted to be forced into the work.

RALPH A HENDRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

